This invention relates to a spray cooled system for the side wall and tap hole cover of an eccentric bottom tap (EBT) electric furnace, e.g. an electric arc furnace having a generally circular hearth portion, below one or more electrodes, in which steel scrap is melted, and an adjacent eccentrically configured relatively shallow portion which has a valved, bottom tap-hole through which molten steel can exit the furnace upon opening of the valve and tilting of the furnace.
The most common configuration of an EBT furnace comprises a main, "tall" section, which is spray or water-cooled, and positioned above the circular portion of the fiurnace and, an adjacent lower EBT (eccentric) extension that includes the "sand hole" through which sand is poured to cover and protect the tap hole valve of the fuxnace. The "tall" section is provided with a removable, circular water-cooled or spray cooled roof and scrap metal is charged to the furnace and melted beneath the roof. Upon completion of melting the entire furnace is tilted toward the eccentric (tap) portion with the tap valve is open to allow molten steel to be discharged from the furnace into a ladle positioned below the furnace. When tapping is completed, the taphole valve is closed and the furnace is leveled. Sand is then poured through the sand hole in the cover and into the tap-hole in the refractory hearth below to protect the underlying tap-hole valve. The furnace is then ready for melting and tapping the next charge.
The cover for the EBT (eccentric) portion is customarily a pressurized water-cooled panel or a separate spray cooled panel. The water-cooled panel is usually flat and horizontal and includes a sand hole. The separate spray cooled panel is a combination of a sloping plate and a conical portion which allows effective flow of water onto and off the plate. The spray-cooled panel also contains a sand hole and has a spray cooled chamber. In use, the separate spray cooled panel is bolted to the "tall" spray cooled section with each section having it's own coolant supply and independent drains for spent coolant. This type of spray cooled configuration is subject to fume and flame discharge at the joint between the main "tall" section and the EBT cover, and spent coolant can not equalize between the sections.
Another prior commercial arrangement included an egg-shaped roof which covered both the circular and EBT portions of the furnace which resulted in a single, very heavy "tall" section with the sand-hole located in the roof, high above the tap-hole which complicates filling of the tap-hole.